Cable television networks refer to communications networks that are used to transmit cable television signals and/or other information between one or more service providers and a plurality of subscribers, typically over coaxial and/or fiber optic cables. Most conventional cable television networks comprise hybrid fiber-coaxial networks. In these networks, fiber optic cables are typically used to carry signals from the headend facilities of the service provider to various distribution points, while less expensive coaxial cable may be used, for example, to carry the signals into neighborhoods and/or into individual homes, apartment complexes, businesses and other subscriber premises.
Typically, the service provider is a cable television company that may have exclusive rights to offer cable television services in a particular geographic area. The subscribers in a cable television network may include, for example, individual homes, apartments, hotels, businesses, schools, government facilities and various other entities. The service provider may broadcast a broad variety of cable television channels to subscribers over the cable television network. Most cable television service providers also now offer other services such as, for example, broadband Internet service and digital telephone service. Thus, in many cases, a subscriber of the service provider may receive cable television service, a broadband Internet connection, and Voice-over-Internet Protocol (“VoIP”) Internet telephone service all through a single RF connection over the cable television network between the service provider and the subscriber premise.
To provide services to individual subscriber premises, tap units are typically connected in series along communications lines (e.g., a coaxial cable) of the cable television network. These tap units typically have an input port that connects to a first segment of the communications line, an output port that connects to a second segment of the communications line, and one or more RF tap ports. Cables, such as, for example, coaxial cables, may run between each RF tap port of a tap unit and a respective subscriber premise. In this manner, each RF tap port acts as a branch off of the communications line that is used to provide a communications path between the service provider and an individual subscriber premise over the cable television network. RF signals are transmitted through each RF tap port between the cable television network and an individual subscriber premise. Typically, a tap unit will include multiple tap ports (e.g., four or eight RF tap ports).
In residential applications, because of attenuation that occurs as signals are passed through the communications lines of the cable television network and through various connections such as tap units, the power level of the RF signal that is received at subscriber premises may be on the order of 5 dBmV/channel, which may be insufficient to support the various services at an acceptable quality of service level. Accordingly, an RF signal amplifier may be provided at many individual subscriber premises that is used to amplify the RF signal received over the RF connection between the cable television network and the subscriber premises to a more useful level of approximately 20 dBmV/channel. In some cases, the RF signal amplifier may also amplify any RF signals that are transmitted in the reverse direction from the subscriber premise to the cable television network (note that broadband Internet and Internet telephone service both involve full duplex transmissions, as does some types of cable television service such as pay-per-view service). These RF signal amplifiers typically include an RF input port that is connected to an RF tap port of a tap unit by, for example, a coaxial cable, and at least one RF output port. An exemplary RF signal amplifier may include a power divider circuit that provides four or eight RF output ports, as typical subscriber premises include multiple RF wall jacks, each of which requires a separate connection to the cable television network. Each RF signal amplifier includes one or more power amplifiers that are used to amplify the RF signals that pass therethrough. A direct current (“DC”) power connection is also provided, either through a separate power input port or through one of the RF output ports (an output port may be configured to provide both the DC power connection and to pass RF signals). The DC power connection is used to power the power amplifiers that amplify the RF signals that are passed through the RF signal amplifier.
Unfortunately, if the power connection to the RF signal amplifier is interrupted, the power amplifiers cease operating, and RF signals hence cease to pass through the power amplifiers. As a result, service between the cable television network and the subscriber premise is interrupted. Although such interruptions may be tolerated by consumers in relation to certain non-essential services, interruptions to other services may be unacceptable. For example, consumers relying on IP-based emergency communications (i.e., Internet telephone 911 service) can be left without such services during power interruptions.